fix corrupt prefs when the file already exists

undetected_chromedriver/__init__.py

@@ -375,6 +375,7 @@ class Chrome(selenium.webdriver.chrome.webdriver.WebDriver):
                     config["profile"]["exit_type"] = None
                 fs.seek(0, 0)
                 json.dump(config, fs)
+                fs.truncate()  # the file might be shorter
                 logger.debug("fixed exit_type flag")
         except Exception as e:
             logger.debug("did not find a bad exit_type flag ")

undetected_chromedriver/options.py

@@ -39,6 +39,20 @@ class ChromeOptions(_ChromiumOptions):
             value = ChromeOptions._undot_key(rest, value)
         return {key: value}
 
+    @staticmethod
+    def _merge_nested(a, b):
+        """
+        merges b into a
+        leaf values in a are overwritten with values from b
+        """
+        for key in b:
+            if key in a:
+                if isinstance(a[key], dict) and isinstance(b[key], dict):
+                    ChromeOptions._merge_nested(a[key], b[key])
+                    continue
+            a[key] = b[key]
+        return a
+
     def handle_prefs(self, user_data_dir):
         prefs = self.experimental_options.get("prefs")
         if prefs:
@@ -55,7 +69,7 @@ class ChromeOptions(_ChromiumOptions):
             prefs_file = os.path.join(default_path, "Preferences")
             if os.path.exists(prefs_file):
                 with open(prefs_file, encoding="latin1", mode="r") as f:
-                    undot_prefs.update(json.load(f))
+                    undot_prefs = self._merge_nested(json.load(f), undot_prefs)
 
             with open(prefs_file, encoding="latin1", mode="w") as f:
                 json.dump(undot_prefs, f)